Otherworldly artwork

Dust devil tracks on Mars

Tracks left by dust devils moving across the Martian dune plains.

These amazing patterns were spotted in the northern hemisphere of Mars on August 24, 2009 by the HiRISE camera aboard NASA’s orbiting Mars Reconnaissance Orbiter (MRO) spacecraft.

They are the tracks left by dust devils—mini tornadoes—moving across the Martian dunes.

Satellite image of a Martian dust devil

Looking down on a Martian dust devil...the small, round fuzz ball near the bottom left corner. The shadow cast by the devil can be seen to its left.

Take a look at the high-resolution version (will open in a new window or tab) of the image—it’s quite amazing.

Dust devils form when the Sun heats the surface so that the ground is warm to the touch, even though the atmosphere at 2 metres (6 feet) above the surface would be chilly. That temperature contrast causes convection (rising air) to where the wind speed is slightly higher. Mixing the dust, winds, and convection triggers the dust devils.

Scientists use images of dust devils to study several things. Tracking the devils shows which way the wind blows at different times of day. Statistics on the size of typical dust devils will help with estimates of how much dust they pump into the atmosphere every day. And by watching individual devils change as they go over more-dusty and less-dusty terrain, researchers can learn about the turbulent motion near the surface. Ultimately, that motion of wind and dust near the surface relates these small dust devils with Mars’ much larger dust storms.

MRO was 285 kilometres above the Martian surface at the time it took the image, which shows detail down to about 1.7 metres resolution.

The video below shows the progress of a dust devil moving across the plains in full view of the Spirit lander. The sequence of images spans a period of 9 minutes and 35 seconds, but has been speeded up for the purposes of the video.

Adapted from information issued by NASA / JPL-Caltech / Cornell University / Texas A&M / University of Arizona.

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